For polio, two vaccines are better than one

22 August 2014

A child receives oral polio vaccine drops from a house-to-house polio vaccination team in Bihar, India.

Image: A child receives oral polio vaccine drops from a house-to-house polio vaccination team in Bihar, India. ©  Gates Foundation/Flickr (CC BY-NC-ND 2.0)

Using both live and inactivated polio vaccines could help speed the global eradication of polio, a new study reports.

The study, done in Indian children already given the live polio vaccine, shows that a single dose of the inactivated vaccine boosts immunity more effectively than an additional live vaccine dose.

The results have already contributed to a decision by World Health Organisation (WHO) advisers to use the inactivated vaccine more widely in the push to eradicate polio.

In certain parts of the globe, like Pakistan and Nigeria, polio is proving difficult to eradicate. Making the choice between an oral live attenuated vaccine (OPV) and an injected inactivated vaccine (IPV) has been highly controversial.

To date, OPV has been more widely used because it is cheaper, requires no needles to administer, and is better able to induce immunity in the intestinal lining, known as mucosal immunity. However, the immune response to OPV is highly variable and mucosal immunity appears to diminish rapidly after OPV, meaning that several doses of this vaccine may be required, a difficult feat in remote or conflict zones.

Professor Nick Grassly from Imperial College London said: "The decision to use inactivated poliovirus vaccine was previously controversial because it was unclear whether it would improve intestinal immunity. But in the last year we've published two studies that have provided convincing evidence that when given to children who previously received oral vaccine, the inactivated vaccine offers a very effective boost.

"This means that both OPV and IPV have an important role to play in the eradication programme. The results have already fed into the WHO's eradication strategy, and campaigns with the vaccine have started in Nigeria and are planned for Pakistan, two countries with persistent poliovirus transmission."

Researchers led by the WHO tested whether use of OPV or IPV would improve mucosal immunity. They conducted a randomised clinical trial in northern India in which almost 1,000 infants and children were given one vaccine or the other.

After four weeks, all the participants were given a "challenge" with the live-attenuated OPV to test whether they were protected against infection. In those who had received IPV, the amount of virus shed in stools after OPV was greatly reduced, meaning these children were less infectious to others. The IPV group also produced more antibodies, meaning these individuals are better protected against polio disease.

The paper, Efficacy of Inactivated Poliovirus Vaccine in India, is published in Science.

  • In children who've already had the live polio vaccine, a single dose of inactivated vaccine boosts immunity to the disease more effectively than another dose of live vaccine, according to new research. 
  • Until now, the live vaccine has been used more widely as it is given orally (meaning no needles are needed), is cheaper and was thought to be more effective at inducing immunity in the intestinal lining. Now however, the World Health Organization is pushing the inactivated virus as a booster instead.